Precision rectangular perforation on photographic film edges is required to advance or rewind films in cameras or projection of movie films on the screen. During perforation of the photographic film, the photographic film rides over the outer surface of a series of rollers. This necessitates a hard and wear resistant outer surface for the rollers. The rollers are typically chrome plated stainless steel. The outer surface finish is very critical in that rollers should not scratch the photographic films. Thin chrome plating generally provides an adequate hard wear resistant surface which does not produce scratches on the photographic film. Thick chrome plating, however, generates a rough surface and is not used for rollers transporting photographic film. In addition, the rollers in the perforator rotate on a hardened steel pin. Typical inside diameters of the rollers are 60 to 70 thousandths of an inch. The small inner diameters of rollers are too narrow to provide a uniform chrome plating and that in turn limits the service life of conveyance rollers.
Moreover, photographic film contains corrosive silver halide salts which attack stainless steel through microcracks and pores in the chrome plating. The corrosion products along with the wear debris tend to contaminate the films and also accumulate between the pin and the inner surface of the roller, thus, reducing clearance and jamming the transportation process. Wear of the pin and roller causes excessive runout and the perforating machines need to be stopped and overhauled frequently.
The present invention replaces the chrome plated stainless steel rollers with yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic which rotate on hardened steel pins. Superior wear and corrosion resistance of the Y-TZP ceramic make these rollers more productive than chrome plated steel rollers. In addition, the absence of corrosion products and the lessening of steel pin wear reduces debris and helps reduce film contamination and prolongs the service life of the perforating machine.